When a jet-powered aircraft lands, the landing gear brakes and aerodynamic drag (e.g., flaps, spoilers, etc.) of the aircraft may not, in certain situations, be sufficient to slow the aircraft down in the required amount of runway distance. Thus, jet engines on most aircraft include thrust reversers to enhance the braking of the aircraft. When deployed, a thrust reverser redirects the rearward thrust of the jet engine to a generally or partially forward direction to decelerate the aircraft. Because at least some of the jet thrust is directed forward, the jet thrust also slows down the aircraft upon landing.
Various thrust reverser designs are commonly known, and the particular design utilized depends, at least in part, on the engine manufacturer, the engine configuration, and the propulsion technology being used. Thrust reverser designs used most prominently with jet engines fall into three general categories: (1) cascade-type thrust reversers; (2) target-type thrust reversers; and (3) pivot door thrust reversers. Each of these designs employs a different type of moveable thrust reverser component to change the direction of the jet thrust.
Cascade-type thrust reversers are normally used on high-bypass ratio jet engines. This type of thrust reverser is located on the circumference of the engine's midsection and, when deployed, exposes and redirects air flow through a plurality of cascade vanes. The moveable thrust reverser components in the cascade design includes several translating sleeves or cowls (“transcowls”) that are deployed to expose the cascade vanes.
Target-type reversers, also referred to as clamshell reversers, are typically used with low-bypass ratio jet engines. Target-type thrust reversers use two doors as the moveable thrust reverser components to block the entire jet thrust coming from the rear of the engine. These doors are mounted on the aft portion of the engine and may form the rear part of the engine nacelle.
Pivot door thrust reversers may utilize four doors on the engine nacelle as the moveable thrust reverser components. In the deployed position, these doors extend outwardly from the nacelle to redirect the jet thrust.
The moveable thrust reverser components in each of the above-described designs are moved between the stowed and deployed positions by actuators. Power to drive the actuators may come from a dual output power drive unit (PDU), which may be electrically, hydraulically, or pneumatically operated, depending on the system design. A drive train that includes one or more drive mechanisms, such as flexible rotating shafts, may interconnect the actuators and the PDU to transmit the PDU's drive force to the moveable thrust reverser components.
The primary use of thrust reversers is, as noted above, to enhance the braking of the aircraft, thereby shortening the stopping distance during landing. Hence, thrust reversers are usually deployed during the landing process to slow the aircraft. Thereafter, when the thrust reversers are no longer needed, they are returned to their original, or stowed, position. Once in the stowed position, one or more locks are engaged to prevent unintended movement of the thrust reversers and/or actuators that move the thrust reversers.
Although the number of locks may vary, many thrust reverser systems include primary, secondary, and tertiary locks. Depending on thrust reverser system configuration, one or more primary locks may be coupled to one or more of the actuators, one or more secondary locks (or “brakes”) may be coupled to the PDU, and one or more tertiary locks may be coupled to one or more of the thrust reversers.
In some thrust reverser systems, the tertiary locks may be electromechanical type of locks that receive AC electrical power from the aircraft power system. The AC electrical power from the aircraft power system, which is typically around a nominal value of 115 VAC, may be converted to a DC power signal having a much lower voltage magnitude. This DC power signal is in turn used to control the tertiary locks. The aircraft power system may fluctuate, both above and below, the nominal voltage magnitude, which may cause the DC power signal supplied to the tertiary locks to also fluctuate above and below a nominal magnitude. If the DC power signal fluctuates too low below the nominal voltage magnitude, the tertiary locks may not release. If the DC power signal fluctuates too high above the nominal magnitude, one or more components of the tertiary locks can overheat and/or otherwise be damaged.
Hence, there is a need for a tertiary lock system that can accommodate voltage fluctuations in an aircraft power system while supplying DC power to a tertiary lock in a manner that does not prevent the tertiary locks from releasing when commanded to do so, and/or that does not result in one or more components of the tertiary locks overheating and/or otherwise becoming damaged. The present invention addresses at least this need.